I took this question to Bill Nowlin, one of the co-founders of Rounder Records. To provide a frame of reference, I asked him to consider the question with regard to Rounder's North American Traditions series. You can view that series' great website here , to see what I'm talking about. It contains mostly (perhaps exclusively?) instumental albums by community masters--great amateur musicians given professional recordings. With respect to that series, Bill said, "Almost any good, straightahead, strictly traditional record would have sold 1500 to 2000 copies in the later 1970s. Now, sales might be more like 250." He added that there is very little opportunity today for someone to find this type of material at retail. He hopes that quality websites and download services--and ways for people to find them--could serve whatever interest exists for such recordings. He believes (maybe he hopes) that the interest for such material remains strong.

Cheers,
Michael Scully
Austin